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Reducing road noise

The tires on my car sound like the old snow tires of the past. I have been told this is a problem with year (2008)car which I purchased Used. The new model has added noise dampening material which made an improvement. Do you think under coasting would help this situation? If so, what should be the composition of the material used? Where should the Under Coasting be placed?

Aha! Finally a subject I know something about!

Undercoating will do little to help. Been there, done that.

I drive a 2005 Scion tC. love the car, but it’s a hatchback and has always been road noisy. Recently I pulled the rear interior panels to access the upper shock mount bolts for a shock absorber replacement. Before I replaced any of them, I decided to add sound deadener. There was almost no insulation under the panels.

I did a bit of research and ordered a structural sound damper from Second Skin. The parts store carries one called Dynamat, but the Second Skin was a lot less costly and the same stuff. I lined the sheetmetal with the structural damper and carpeted over it with an industrial quality carpet from WalMart.

The difference is phenominal. I don’t even turn up my radio on the highway anymore. I just did it a week or so ago, and was initially reticent to sound too enthusiastic about the results, but now I’m absolutely convinced. I’ve now picked up some jute (carpet padding) and have decided to pull the rear seat bottom, remove the rear seat sidepanels and the kickpanels, and do those areas as well.

In my car I had a flat panel in the rear to cover the spare tire and tools, create a flat floor with the seats down, and mask some of the road noise. When I did the job I carpeted the recesssed areas by the spare and left the fllat cover off to see how it’d be. It’s so quiet I’m not replacing the flat panel. I’m using the recesses like a trunk floor now.


  1. that road noise is sometimes called “white noise” by acoustics engineers. It’s a backround noise that can mask other noises. If you have any wind noise, and rattles, any pther noises, be prepared to start noticing them. You’ll have to accept this.

  2. I recommend getting a body manual from the local dealer. Knowing where all the clips and crews are is an ENORMOUS asset. I wouldn;t try this without knowing where I was headed. In my case I was able to find a Scion tC site with “exploded view” drawings of the interior assemblies.

Note that in over 40 years of owning and working on cars this is the first time I’ve ever done this. I’m still having a hard time admitting to myself how much of a difference it’s made. I sound like an excited young kid exaggerating, but I’m actually a pragmatic old codger providing an accurate description.

My recommendation? Second Skin (or dynamat) on the sheetmetal covered by jute and industrial carpeting.

[b] My recommendation? Second Skin (or dynamat) on the sheetmetal [/b]  Worth repeating.  

I would avoid undercoating  Back in the 70's it was a good idea, but modern cars have a complex anti rust system and adding undercoating can cause rust problems.  The undercoating material can block the carefully engineered drains and end up making the rust worse.  

That said, I would want to try a different set of tyres. 

How much history do you know about when it comes to the tyres that are there now?

How long did it take you to get all that done?

This could also be a mechanical problem or tire problem. You may have a wheel bearing, or more than one wheel bearing, going bad or you could have cupping or feathering of your tires, or even a defective tire. Bad wheel bearings are common these days and can be described as sounding like driving on old snow tires or even driving on rumble strips. Often, if it’s just one wheel bearing, you can narrow it down by veering back and forth on the highway, carefully of course. If the noise goes away when you veer to the right, it’s on the right side, and vice versa.